Rudy Giuliani dropped an ominous hint about whether a Trump-Mueller interview is going to happen

Rudy Giuliani said he thinks there is a "50/50" chance special counsel Robert Mueller will subpoena President Donald Trump to testify before a grand jury.

Mueller is investigating Russian interference in the 2016 US election, the Trump campaign's possible involvement, and whether Trump obstructed justice after the Russia probe began.

Giuliani's remark on Thursday night followed an earlier report that Mueller threatened Trump with a subpoena if he refused to speak to the special counsel under oath.

The revelation sheds more light on whether Trump will voluntarily oblige Mueller's request for an interview.

Rudy Giuliani said he believes there is a "50/50" chance special counsel Robert Mueller will subpoena President Donald Trump to testify before a grand jury as part of the Russia probe.

Mueller is investigating Russian interference in the 2016 US election, the Trump campaign's possible involvement, and whether Trump obstructed justice after the probe began. Trump's attorneys have been in ongoing negotiations with Mueller's team for a one-on-one interview with the president.

While Trump has, in fits and starts, expressed his willingness to sit down with Mueller, he pulled back a bit more recently, after his longtime personal attorney, Michael Cohen's property was raided by the FBI last month in an unrelated case.

Since Giuliani joined Trump's legal team, he has floated some possible parameters for a Trump-Mueller interview, including limiting the duration of such a meeting and narrowing the scope of the questions Mueller may ask.